The ultimate example of luxury emissions is probably private spaceflight, as described in Nature recently. All that fuel gets burned so that a few really rich people can get to a high altitude and gawk for a while before returning to Earth.

I entirely agree with the sentiment here (ditch luxuries before necessities) and that space tourism represents one of the ultimate luxuries. However, a small pedantic note: certain types of common rocket propellant do not directly produce carbon emissions (for instance liquid oxygen and hydrogen, which combine to form H20).* Of course, the production of these substances requires energy, which is likely to have come from burning fossil fuels, yet theoretically, they could be produced using renewables and then used to lift rockets without a major carbon footprint.

*Yes, water vapour is of course also a GHG, but its short residency means that adding small amounts of water vapour to the atmosphere is not really a climate issue. It is a feedback, not a forcing.

The industry’s worst fears, of a collapse in cruise bookings, proved to be misplaced. Worldwide, cruise ships’ passenger numbers rose in 2012 and 2013, in spite of the accidents. And Carnival remained profitable, as did its two main rivals, Royal Caribbean International (RCL) and Norwegian Cruise Lines (NCL). Revenues were hit, but they have begun to bounce back. Carnival’s revenues started to rise again in 2013, and analysts also expect both RCL and NCL to report strong growth this year.

Space tourism is, charitably, an indulgence for the super-rich. As for colonising other planets, there’s a reason they call that stuff science fiction. As millions on Earth die from preventable illness, poor sanitation and famine, technologies that serve alleged convenience and fantasy are irresponsible, not laudable.

I am encouraged to see that you have retained your admirable scepticism in most other regards. But if you must keep at it with plutocrats in orbit (and robotic cars, which won’t make a material dent on the highways until the 2030s, if ever), may I suggest that for convenience you centralise the articles in a new section. Perhaps you could title it Implausibilities and improbabilities.